Lithium cobalt oxide, method for manufacturing the same, and nonaqueous electrolyte secondary battery

Abstract

Lithium cobalt oxide, which can provide a nonaqueous electrolyte secondary battery having an excellent initial capacity and an excellent capacity retention, and a method for manufacturing the same are provided. The lithium cobalt oxide has a tap density of at least 1.7 g/cm 3 and a pressed density of 3.5 to 4.0 g/cm 3 . A method for manufacturing the lithium cobalt oxide includes the step of selecting a lithium cobalt oxide (A) and a lithium cobalt oxide (B) so that a difference in the tap density between the lithium cobalt oxide (A) and the lithium cobalt oxide (B) is at least 0.2 g/cm 3 ; and mixing the lithium cobalt oxide (A) and the lithium cobalt oxide (B).

1. Lithium cobalt oxide comprising:
 a mixture of lithium cobalt oxide particles (A) and lithium cobalt oxide particles (B); 
 wherein the lithium cobalt oxide particles (A) are composed of uniformly monodisperse particles, which refers to particles present independently of each other, and the lithium cobalt oxide particles (A) have an average particle diameter in a range of 5 to 30 μm; 
 the lithium cobalt oxide particles (B) are composed of an aggregation of primary particles forming a secondary particle, and the secondary particles have an average particle diameter in a range of 0.1 to 10 μm; and 
 wherein a tap density of the mixture of the lithium cobalt oxide particles (A) and the lithium cobalt oxide particles (B) is at least 1.7 g/cm 3 , and a pressed density of the mixture of the lithium cobalt oxide particles (A) and the lithium cobalt oxide particles (B) is 3.5 to 4.0 g/cm 3 . 
 
     
     
       2. The lithium cobalt oxide according to  claim 1 , wherein the tap density of the mixture of the lithium cobalt oxide (A) and the lithium cobalt oxide particles (B) is at least 2.0 g/cm 3  and the pressed density of the mixture of the lithium cobalt oxide (A) and the lithium cobalt oxide particles (B) is 3.6 to 4.0 g/cm 3 . 
     
     
       3. The lithium cobalt oxide according to  claim 1 , wherein the tap density of the mixture of the lithium cobalt oxide (A) and the lithium cobalt oxide particles (B) is 2.5 to 3.5 g/cm 3  and the pressed density of the mixture of the lithium cobalt oxide (A) and the lithium cobalt oxide particles (B) is 3.7 to 4.0 g/cm 3 . 
     
     
       4. The lithium cobalt oxide according to  claim 1 , wherein an average particle diameter of the lithium cobalt oxide particles (B) is smaller than an average particle diameter of the lithium cobalt oxide particles (A) in the mixture of the lithium cobalt oxide particles (A) and the lithium cobalt oxide particles (B). 
     
     
       5. A nonaqueous electrolyte secondary battery comprising a cathode plate having a cathode active material, wherein the cathode active material includes a mixture of lithium cobalt oxide particles (A) and lithium cobalt oxide particles (B);
 the lithium cobalt oxide particles (A) are composed of uniformly monodisperse particles, which refers to particles present independently of each other, and the lithium cobalt oxide particles (A) have an average particle diameter in a range of 5 to 30 μm; 
 the lithium cobalt oxide particles (B) are composed of an aggregation of primary particles forming a secondary particle, and the secondary particles have an average particle diameter in a range of 0.1 to 10 μm; and 
 wherein a tap density of the mixture of the lithium cobalt oxide particles (A) and the lithium cobalt oxide particles (B) is at least 1.7 g/cm 3 , and a pressed density of the mixture of the lithium cobalt oxide particles (A) and the lithium cobalt oxide particles (B) is 3.5 to 4.0 g/cm 3 . 
 
     
     
       6. The nonaqueous electrolyte secondary battery according to  claim 5 , wherein a ratio of the mixture of the lithium cobalt oxide particles (A) and the lithium cobalt oxide particles (B) is (A):(B)=95:5 to 60:40 on a weight basis. 
     
     
       7. The nonaqueous electrolyte secondary battery according to  claim 5 , wherein a ratio of the mixture of the lithium cobalt oxide particles (A) and the lithium cobalt oxide particles (B) is (A):(B)=90:10 to 80:20 on a weight basis. 
     
     
       8. The nonaqueous electrolyte secondary battery according to  claim 5 , wherein the average particle diameter of the lithium cobalt oxide particles (A) is within the range of 10 to 20 μm. 
     
     
       9. The nonaqueous electrolyte secondary battery according to  claim 5 , wherein the average particle diameter of the lithium cobalt oxide particles (B) is within the range of 2.0 to 8.0 μm. 
     
     
       10. The nonaqueous electrolyte secondary battery according to  claim 5 , wherein the pressed density of the mixture of the lithium cobalt oxide particles (A) and the lithium cobalt oxide particles (B) is 3.6 to 4.0 g/cm 3 . 
     
     
       11. The nonaqueous electrolyte secondary battery according to  claim 5 , wherein the pressed density of the mixture of the lithium cobalt oxide particles (A) and the lithium cobalt oxide particles (B) is 3.7 to 4.0 g/cm 3 . 
     
     
       12. The nonaqueous electrolyte secondary battery according to  claim 5 , wherein the tap density of the mixture of the lithium cobalt oxide particles (A) and the lithium cobalt oxide particles (B) is 2.0 to 3.0 g/cm 3 . 
     
     
       13. The nonaqueous electrolyte secondary battery according to  claim 5 , wherein an average particle diameter of the lithium cobalt oxide particles (B) is smaller than an average particle diameter of the lithium cobalt oxide particles (A) in the mixture of the lithium cobalt oxide particles (A) and the lithium cobalt oxide particles (B).